A wireless energy transfer technology, which is a latest technology capable of supplying power anytime and anywhere even without an electric cable, is expected as a future technology having potential over the present wireless communication technology In the wireless energy transfer technologies of the related art, for example, there are an electromagnetic inductive type using electromagnetic induction, an electromagnetic resonance type using electromagnetic resonance, and a microwave type.
The electromagnetic inductive type, one of the technologies of the related art, generates electromotive force on one coil of two adjacent coils by means of magnetic flux that is generated when current is applied to the other coil, using two electromagnetic inductances. In this type of electromagnetic induction, there is a need of sensing and protecting against metallic foreign substances due to magnetic inductive heat, deterioration of electric characteristics such as interference is caused by influence on the noise characteristic of other electronic devices, and the problem with the lifespan due to heat generation and chemical reaction in charging of a battery has been pointed out, and especially, the concern about harmfulness to the human has a latent problem and causes an argument about safety. Further, the energy transfer range limited to several millimeters to several centimeters has been pointed out as a critical problem of the electromagnetic induction type.
The electromagnetic resonance type, another type of technology, has the operation range increased up to 4 m in comparison to the electromagnetic inductive type, using non-radiative resonance, but the short available distance is still a problem in the actual operation and a low transmission efficiency due to the loss of the heat and the electric wave of the electromagnetic field has been pointed as an obstacle to spread of the energy transfer technology.
Further, it cannot be applied to large-capacity consumer electronics (CE) having capacity of over tens of watts, including a television, due to low transfer efficiency and a distance limit.
Due to those problems of the related art, there is a need of a new type of wireless energy transfer technology that has a wide wireless energy transfer range and can stably supply energy with high energy transfer efficiency without harmfulness to the human body.